【摘 要】
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Since1963ithasbeenwellestablishedthatsomesurfacesoilscontaindifficultlyextractablefixedammonium(DEFA)whichcannotbedeterminedbyKjeldahlprocedurescommonlyusedforsoils(StewartandPorter,1963;KeeneyandBrem
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Since1963ithasbeenwellestablishedthatsomesurfacesoilscontaindifficultlyextractablefixedammonium(DEFA)whichcannotbedeterminedbyKjeldahlprocedurescommonlyusedforsoils(StewartandPorter,1963;KeeneyandBremner,1967).However,itisnotknownuntilnowinwhatsoilty
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